I don't believe Truman ran in '52. Ike ran against some wreck of Democrat (Stevenson?) and won handily.
You're correct. It was Adalai Stevenson & Ike in '52. I believe Truman declined the Dems nomination in '52 because of the Dems trying to get Ike to run as a Dem. Ike creamed them as a Repub.
I do, however, stand by the crux of my point and recall that LBJ feared what happened to Truman would happen to him. From 1952 to 1964 was not a long time in the political mind of LyndonJohnson. A self fulfilling prophesy, to be sure.